Had u seen a doctor for it to find out the cause of the rash like appearance? If if could be fungal or dermatitis or something? I used "pot of gold" baby balm version. The other one that is also good is the Tiny Tree pure coconut balsam. A thin layer a few days and my boy recovered - also neck area. Get well soon little one
I heard some mama uses corn starch to keep the neck area dry. It's not as fine as talc powder so safer. Or you can try those liquid powder.
I use my diaper rash cream it works on most rash